That denial might be the relevant one:
Sep 26 14:49:10 ubuntu kernel: [ 53.916666] audit: type=1400 audit(1411735750.942:62): apparmor="DENIED" operation="socket_shutdown" profile="/usr/lib/chromium-browser/chromium-browser//chromium_browser_sandbox" pid=2965 comm="chrome-sandbox" family="unix" sock_type="stream" protocol=0 requested_mask="shutdown" denied_mask="shutdown" addr=none
That denial might be the relevant one:
Sep 26 14:49:10 ubuntu kernel: [ 53.916666] audit: type=1400 audit(141173575 0.942:62) : apparmor="DENIED" operation= "socket_ shutdown" profile= "/usr/lib/ chromium- browser/ chromium- browser/ /chromium_ browser_ sandbox" pid=2965 comm="chrome- sandbox" family="unix" sock_type="stream" protocol=0 requested_ mask="shutdown" denied_ mask="shutdown" addr=none